In satellite communications, a plurality of signals modulated on multiple carriers that span a given frequency band are combined and applied to a last stage power amplifier. The composite multi-carrier signal has a large variation in amplitude, which is characterized by a large peak-to-average power ratio.
A challenge for power amplifiers is providing the required RF power or amplification with high linearity and efficiency. Linearity can be measured by the ratio of the desired signal and all undesired intermodulation products at the output of the amplifier. Efficiency can be measured by the ratio of the RF signal power delivered at the output of the amplifier and the total DC power required by the amplifier. Linearity and efficiency tend to move in opposite directions in practical amplifiers. Highly linear amplifiers such as Class A amplifiers have lower efficiencies than non-linear amplifiers. Non-linear amplifiers such as Class C amplifiers have higher efficiencies but may produce unacceptable levels of in-band and adjacent-band intermodulation products.
Accordingly, it is desirable to suppress the non-linear intermodulation products of non-linear amplifiers to provide linear and efficient amplifiers.